Thiophanate-methyl and triazole-based compounds such as tebuconazole are known as active ingredients for agricultural and horticultural chemicals. Moreover, thiophanate-methyl is known form a crystalline complex (Patent Document 1). Since the dissolution property or the like changes by the formation of a crystalline complex, that is to say, co-crystal, use of such a co-crystal as a raw material for an agricultural and horticultural chemical composition has been studied.